U.S. patent application number 13/075783 was filed with the patent office on 2012-10-04 for method for producing ethylene-vinyl alcohol copolymer resin, ethylene-vinyl alcohol copolymer resin, and multilayer structure.
This patent application is currently assigned to KURARAY CO., LTD.. Invention is credited to Robert Armstrong, Ray Jouett, Toshio TSUBOI, Yoshio Yamamoto.
Application Number | 20120248640 13/075783 |
Document ID | / |
Family ID | 46926130 |
Filed Date | 2012-10-04 |
United States Patent
Application |
20120248640 |
Kind Code |
A1 |
TSUBOI; Toshio ; et
al. |
October 4, 2012 |
METHOD FOR PRODUCING ETHYLENE-VINYL ALCOHOL COPOLYMER RESIN,
ETHYLENE-VINYL ALCOHOL COPOLYMER RESIN, AND MULTILAYER
STRUCTURE
Abstract
Provided is by the present invention is a method for producing
an EVOH resin having sufficient long-run workability in melt
molding and enabling prevention of coloring such as yellowing, an
EVOH resin obtained by this method for production, and a laminate
obtained from this resin. The present invention is a method for
producing an ethylene-vinyl alcohol copolymer resin, the method
including a step of saponifying an ethylene-vinyl ester copolymer
to obtain an ethylene-vinyl alcohol copolymer, in which the method
is characterized by further including a step of irradiating the
ethylene-vinyl ester copolymer or the ethylene-vinyl alcohol
copolymer with an infrared ray.
Inventors: |
TSUBOI; Toshio; (Pasadena,
TX) ; Jouett; Ray; (Pasadena, TX) ; Armstrong;
Robert; (Pasadena, TX) ; Yamamoto; Yoshio;
(Kurashiki-shi, JP) |
Assignee: |
KURARAY CO., LTD.
Kurashiki-shi
JP
|
Family ID: |
46926130 |
Appl. No.: |
13/075783 |
Filed: |
March 30, 2011 |
Current U.S.
Class: |
264/5 ;
522/150 |
Current CPC
Class: |
B29B 7/726 20130101;
B29B 7/90 20130101; B29B 9/06 20130101; B29B 9/12 20130101; C08F
8/12 20130101; B29B 7/007 20130101; B29B 7/38 20130101; C08F
2810/50 20130101; C08F 8/12 20130101; C08F 210/02 20130101 |
Class at
Publication: |
264/5 ;
522/150 |
International
Class: |
C08J 3/12 20060101
C08J003/12; C08J 3/28 20060101 C08J003/28 |
Claims
1. A method for producing an ethylene-vinyl alcohol copolymer
resin, the method comprising a step of saponifying an
ethylene-vinyl ester copolymer to obtain an ethylene-vinyl alcohol
copolymer, which method further comprising a step of irradiating
the ethylene-vinyl ester copolymer or the ethylene-vinyl alcohol
copolymer with an infrared ray.
2. The method for producing an ethylene-vinyl alcohol copolymer
resin according to claim 1, wherein the irradiation with an
infrared ray in the step of irradiation with an infrared ray is
carried out with an infrared ray lamp.
3. The method for producing an ethylene-vinyl alcohol copolymer
resin according to claim 1, wherein the wavelength of the infrared
ray in the step of irradiation with an infrared ray is 700 nm or
greater and 1,000,000 nm or less.
4. The method for producing an ethylene-vinyl alcohol copolymer
resin according to claim 1, wherein the intensity of the infrared
ray in the step of irradiation with an infrared ray is
30.times.10.sup.3 W/m.sup.3 or greater and 3,000.times.10.sup.3
W/m.sup.3 or less.
5. The method for producing an ethylene-vinyl alcohol copolymer
resin according to claim 1, wherein the irradiation time in the
step of irradiation with an infrared ray is 0.1 hrs or longer and
20 hrs or shorter.
6. The method for producing an ethylene-vinyl alcohol copolymer
resin according to claim 1, wherein the step of irradiation with an
infrared ray is carried out not before the saponification step, and
the temperature of the ethylene-vinyl alcohol copolymer resin in
this step of irradiation with an infrared ray is the glass
transition point or greater and the melting temperature or less of
the ethylene-vinyl alcohol copolymer.
7. The method for producing an ethylene-vinyl alcohol copolymer
resin according to claim 1, wherein the step of irradiation with an
infrared ray is carried out prior to the saponification step, and
the temperature of the ethylene-vinyl ester copolymer resin in this
step of irradiation with an infrared ray is 40.degree. C. or
greater and 110.degree. C. or less.
8. The method for producing an ethylene-vinyl alcohol copolymer
resin according to claim 1, further comprising a pelletization step
of obtaining a hydrous pellet including an ethylene-vinyl alcohol
copolymer from a solution containing the ethylene-vinyl alcohol
copolymer obtained by the saponification step, wherein the step of
irradiation with an infrared ray is carried out not before the
pelletization step.
9. The method for producing an ethylene-vinyl alcohol copolymer
resin according to claim 8, wherein the irradiation with an
infrared ray is carried out on the hydrous pellet, and the water
content of this hydrous pellet before irradiating with an infrared
ray is 10% by mass or greater and 200% by mass or less.
10. The method for producing an ethylene-vinyl alcohol copolymer
resin according to claim 8, further comprising a drying step of
drying the hydrous pellet to obtain a dry pellet having a water
content of 0.01% by mass or greater and less than 10% by mass,
wherein the step of irradiation with an infrared ray is carried out
not before the drying step.
11. The method for producing an ethylene-vinyl alcohol copolymer
resin according to claim 10, wherein the dry pellet has a water
content before irradiating with an infrared ray of 0.01% by mass or
greater and less than 10% by mass.
12. The method for producing an ethylene-vinyl alcohol copolymer
resin according to claim 10, further comprising a molding step of
molding the dry pellet to obtain a molded product including an
ethylene-vinyl alcohol copolymer, wherein the step of irradiation
with an infrared ray is carried out not before the molding
step.
13. The method for producing an ethylene-vinyl alcohol copolymer
resin according to claim 12, wherein the molded product has a water
content before irradiating with an infrared ray of 0.01% by mass or
greater and less than 10% by mass.
14. An ethylene-vinyl alcohol copolymer resin obtained by the
method for producing an ethylene-vinyl alcohol copolymer resin
according to claim 1.
15. The ethylene-vinyl alcohol copolymer resin according to claim
14, which does not substantially comprise a polyene compound in a
region from the surface over the depth of 5 nm.
16. The ethylene-vinyl alcohol copolymer resin according to claim
14, wherein the ethylene-vinyl alcohol copolymer has an ethylene
content of 20% by mole or greater and 60% by mole or less.
17. The ethylene-vinyl alcohol copolymer resin according to claim
14, wherein the ethylene-vinyl alcohol copolymer has a degree of
saponification of 90% by mole or greater.
18. The ethylene-vinyl alcohol copolymer resin according to claim
14, which has a pellet form or film form.
19. A laminate having at least one layer comprising the
ethylene-vinyl alcohol copolymer resin according to claim 14.
20. An ethylene-vinyl alcohol copolymer resin, which does not
substantially comprise a polyene compound in a region from the
surface over the depth of 5 nm.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] The present invention relates to a method for producing an
ethylene-vinyl alcohol copolymer resin, an ethylene-vinyl alcohol
copolymer resin obtained by this method for production, and a
laminate having a layer containing this resin.
[0003] 2. Description of the Related Art
[0004] Ethylene-vinyl alcohol copolymers (hereinafter, may be
abbreviated as "EVOH") are superior in oxygen barrier properties,
transparency, oil resistance, antistatic properties, mechanical
strength and the like, and thus have been widely used as various
types of wrapping material and the like such as films, sheets,
vessels, etc.
[0005] These films and the like are usually formed by a melt
molding method. Therefore, EVOH is expected to have superior
appearance characteristics in melt molding (being enabling molded
articles having superior appearances without generation of gels and
seeds (dirt under paint), occurrence of coloring such as yellowing,
and the like to be obtained), long-run workability (a property
capable of obtaining a molded article without change of physical
properties such as viscosity, etc., and without occurrence of fish
eye, streak, etc., if molded for a long period of time), and the
like. In addition, films, sheets and the like are often formed with
a multilayered structure having an EVOH layer for the purpose of
improving oxygen barrier properties and the like. When such a
laminate is to be obtained, a metal salt is often contained in an
EVOH resin in order to improve adhesiveness between layers.
However, it is known that particularly when a metal salt is
included in an EVOH resin, coloring such as yellowing is more
likely to be caused, and thus appearance characteristics are
deteriorated.
[0006] Under such circumstances, in order to improve various
characteristics demanded for EVOH, particularly appearance
characteristics, a variety of processes such as a process of
irradiating EVOH with an ultraviolet ray (see JP-A No. S50-100194)
and a process of irradiating EVOH with a microwave (see JP-A No.
H11-291245) were proposed.
[0007] However, according to these methods for production, coloring
such as yellowing is not sufficiently prevented, and they are
further disadvantageous in running costs being high, influences on
human bodies being significant, difficulty in adjusting the drying
time, and the like. Specifically, for example, when EVOH is
irradiated with an ultraviolet ray, energy of the ultraviolet ray
is so great that significant negative influences on human bodies
may be concerned. Also, when, for example, a microwave is
irradiated, deterioration occurs even if irradiated for a short
time period of time, and is thus disadvantageous in deteriorated
long-run workability.
PRIOR ART DOCUMENTS
Patent Documents
[0008] Patent Document 1: JP-A No. S50-100194 [0009] Patent
Document 2: JP-A No. H11-291245
SUMMARY OF THE INVENTION
[0010] The present invention was made in view of the foregoing
circumstances, and an object of the invention is to provide a
method for producing an EVOH resin having sufficient long-run
workability in melt molding and enabling prevention of coloring
such as yellowing, an EVOH resin obtained by this method for
production, and a laminate obtained from this resin.
[0011] The present inventors found that an EVOH resin enabling
prevention of coloring such as yellowing can be obtained without
deteriorating long-run workability by irradiating an ethylene-vinyl
ester copolymer (hereinafter, may be abbreviated as "EVAc") that is
a precursor of EVOH, or EVOH with an infrared ray. Moreover, the
present inventors thoroughly investigated, and consequently the
present invention was accomplished.
[0012] An aspect of the invention made in order to solve the
foregoing problems is to provide a method for producing an
ethylene-vinyl alcohol copolymer resin, the method comprising
[0013] a step of saponifying an ethylene-vinyl ester copolymer to
obtain an ethylene-vinyl alcohol copolymer, which method further
comprising
[0014] a step of irradiating the ethylene-vinyl ester copolymer or
the ethylene-vinyl alcohol copolymer with an infrared ray.
[0015] According to the method for producing an EVOH resin,
yellowing of the resulting EVOH resin can be prevented without
deteriorating long-run workability by including a step of
irradiation with an infrared ray
[0016] The irradiation with an infrared ray in the step of
irradiation with an infrared ray is preferably carried out with an
infrared ray lamp. Also, in the step of irradiation with an
infrared ray: the wavelength of the infrared ray is preferably 700
nm or greater and 1,000,000 nm or less; the intensity of the
infrared ray is preferably 30.times.10.sup.3 W/m.sup.3 or greater
and 3,000.times.10.sup.3 W/m.sup.3 or less; and the irradiation
time of the infrared ray is preferably 0.1 hrs or longer and 20 hrs
or shorter. When the wavelength, the intensity and irradiation time
of the infrared ray fall within the above range, yellowing of EVOH
can be further prevented. In addition, when irradiation is carried
out with an infrared ray lamp, the conditions and the like can be
readily adjusted.
[0017] When the step of irradiation with an infrared ray is carried
out not before the saponification step, the temperature of the
ethylene-vinyl alcohol copolymer resin in this step of irradiation
with an infrared ray is preferably the glass transition point or
greater and the melting temperature or less of the ethylene-vinyl
alcohol copolymer. Yellowing can be further prevented by
irradiating the EVOH resin with an infrared ray at a temperature
within this range.
[0018] When the step of irradiation with an infrared ray is carried
out prior to the saponification step, the temperature of the
ethylene-vinyl ester copolymer resin in this step of irradiation
with an infrared ray is preferably 40.degree. C. or greater and
110.degree. C. or less. The yellowing can be further prevented by
irradiating the EVAc resin with an infrared ray at a temperature
within this range.
[0019] Provided that the method for production further has a
pelletization step of obtaining a hydrous pellet including an
ethylene-vinyl alcohol copolymer from a solution containing the
ethylene-vinyl alcohol copolymer obtained by the saponification
step, the step of irradiation with an infrared ray is preferably
carried out not before the pelletization step.
[0020] When the irradiation with an infrared ray is carried out on
the hydrous pellet, the water content of this hydrous pellet before
irradiating with an infrared ray is preferably 10% by mass or
greater and 200% by mass or less.
[0021] Provided that the method for production further has a drying
step of drying the hydrous pellet to obtain a dry pellet having a
water content of 0.01% by mass or greater and less than 10% by
mass, the step of irradiation with an infrared ray is preferably
carried out not before the drying step.
[0022] Provided that the method for production further has a
molding step of molding the dry pellet to obtain a molded product
including an ethylene-vinyl alcohol copolymer, the step of
irradiation with an infrared ray is preferably carried out not
before the molding step.
[0023] The dry pellet or the molded product preferably has a water
content before irradiating with an infrared ray of 0.01% by mass or
greater and less than 10% by mass.
[0024] When the step of irradiation with an infrared ray is carried
out not before the saponification step, the yellowing of the
resulting EVOH resin can be further prevented by irradiation with
an infrared ray is carried out under the aforementioned each
condition.
[0025] The ethylene-vinyl alcohol copolymer resin of the present
invention is a resin obtained by the method for producing an
ethylene-vinyl alcohol copolymer resin.
[0026] The ethylene-vinyl alcohol copolymer resin preferably does
not substantially contain a polyene compound in a region from the
surface over the depth of 5 nm.
[0027] The ethylene-vinyl alcohol copolymer has an ethylene content
of preferably 20% by mole or greater and 60% by mole or less, and a
degree of saponification of preferably 90% by mole or greater.
[0028] The ethylene-vinyl alcohol copolymer resin preferably has a
pellet form or film form.
[0029] The laminate of the present invention is a laminate having
at least one layer containing the ethylene-vinyl alcohol copolymer
resin.
[0030] Herein, the term "ethylene-vinyl alcohol copolymer (EVOH)
resin" means a resin containing EVOH as a principal component, and
this resin may contain other component. Further, the form of this
resin is not particularly limited, and may include, for example, a
solid form, liquid form, solution form, and the like.
[0031] As explained in the foregoing, according to the method for
producing an EVOH resin of the present invention, an EVOH resin
that is superior in appearance characteristics of having sufficient
long-run workability in melt molding, and enabling prevention of
coloring such as yellowing can be obtained. Furthermore, according
to the resin obtained by the method for production, various types
of molded products such as pellets, monolayer or multilayer films,
sheets, pipes, vessels and fibers that are superior in appearance
characteristics can be obtained while enabling prevention of
yellowing.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] Hereinafter, preferred embodiments for carrying out the
present invention are explained in detail.
[0033] The method for producing an EVOH resin of the present
invention is characterized in that in a method for producing an
EVOH resin having a saponification step for saponifying an
ethylene-vinyl ester copolymer (EVAc) to obtain an ethylene-vinyl
alcohol copolymer (EVOH), a step of irradiation with an infrared
ray for irradiating the EVAc or EVOH with an infrared ray is
further included.
[0034] <Infrared Ray>
[0035] In the method for production of the present invention, due
to further having a step of irradiation of EVAc or EVOH with an
infrared ray for irradiating with an infrared ray in a production
step of an EVOH resin as described above, coloring such as
yellowing of the resulting EVOH resin is prevented, and an EVOH
resin having further sufficient long-run workability in melt
molding can be obtained. Although the mechanism of achieving such
effects has not been necessarily known, for example, the following
mechanism may be envisaged. Irradiation with an infrared ray
activates movement of molecular chains, and thus polyene compounds
(particularly polyene compounds having 4 to 8 carbon atoms) that
are presumed to be the cause of coloring being present in the resin
are volatilized. Accordingly, coloring such as yellowing is
prevented, and still further generation of fine seeds (dirt under
paint) can be suppressed even in melt molding at a comparatively
high temperature.
[0036] Although the light source used in the step of irradiation
with an infrared ray in the method for production of the present
invention is not particularly limited, an infrared ray lamp is
preferably used in light of favorable operability.
[0037] The wavelength (which is to be the dominant wavelength) of
the infrared ray irradiated is preferably 700 nm or greater and
1,000,000 nm or less. When the wavelength of the infrared ray falls
within this range, the movement of the molecular chain is
activated. In this step, when the wavelength of the light emitted
from the light source has a width, it is preferred that the
wavelength to be the dominant wavelength of the light falls within
this range. The lower limit of the wavelength of the infrared ray
is preferably 700 nm, more preferably 800 nm, still more preferably
900 nm, and particularly preferably 1,000 nm. On the other hand,
the upper limit of the infrared ray wavelength is preferably
1,000,000 nm, more preferably 10,000 nm, still more preferably
4,000 nm, and particularly preferably 2,500 nm. When the wavelength
of the infrared ray is below the lower limit, movement of the
molecular chain in the resin may be less likely to be activated. On
the other hand, when the wavelength of the infrared ray is beyond
the upper limit, a dehydration reaction proceeds to increase double
bonds in the main chain due to excessively elevated temperature of
the resin containing EVAc or EVOH, leading to enhanced coloring,
whereby the appearance may be deteriorated.
[0038] Although the intensity of the infrared ray is not
particularly limited, it is preferably 30.times.10.sup.3 W/m.sup.3
or greater and 3,000.times.10.sup.3 W/m.sup.3 or less. When the
intensity of the infrared ray falls within this range, the polyene
compounds can be efficiently volatilized, and as a result, coloring
such as yellowing can be further prevented.
[0039] The lower limit of the intensity of the infrared ray is
preferably 30.times.10.sup.3 W/m.sup.3, more preferably
100.times.10.sup.3 W/m.sup.3, still more preferably
150.times.10.sup.3 W/m.sup.3, and particularly preferably
240.times.10.sup.3 W/m.sup.3. On the other hand, the upper limit of
the intensity of the infrared ray is preferably
3,000.times.10.sup.3 W/m.sup.3, more preferably
2,000.times.10.sup.3 W/m.sup.3, still more preferably
1,400.times.10.sup.3 W/m.sup.3, and particularly preferably
350.times.10.sup.3 W/m.sup.3. When the intensity of the infrared
ray is smaller than the lower limit, the amount of volatilized
polyene compounds becomes so low that the coloring may not be
sufficiently prevented. On the other hand, when the intensity of
the infrared ray is beyond the upper limit, the dehydration
reaction proceeds to increase the double bonds in the main chain of
EVOH due to excess elevation of the resin temperature, whereby the
appearance may be deteriorated, and handleability may be impaired
as a result of dissolution of the resin.
[0040] In this regard, the intensity of the infrared ray can be
determined by calculating according to the following formula (I)
when a cylindrical vessel charged with a resin prepared as a
solution is irradiated with an infrared ray from above.
[ formula 1 ] Intensity of infrared radation = wattage of infrared
radiation lamp ( distance from the infrared radiation light source
to the vessel ) .times. ( area of the vessel irradiated with the
infrared radiation ) ( I ) ##EQU00001##
[0041] It should be noted that also in the case of resins having a
particulate form such as pellets or a film form, the intensity of
the infrared ray can be calculated according to the above
calculation process.
[0042] The irradiation time of the infrared ray is preferably 0.1
hrs or longer and 20 hrs or shorter. When the irradiation time of
the infrared ray falls within this range, the resin temperature is
elevated to allow the polyene compounds to be volatilized, whereby
occurrence of coloring such as yellowing can be further
prevented.
[0043] Accordingly, in the case of infrared rays, deterioration of
the resin is not found when the irradiation time is 20 hrs or
shorter. Whereas, deterioration of the resin is found for 300 sec
longer when the wavelength of the infrared ray is beyond 1,000,000
nm (for example, microwave); therefore, it is concluded that the
irradiation time of the irradiation with an infrared ray can be
easily adjusted.
[0044] The lower limit of the irradiation time of the infrared ray
is preferably 0.1 hrs, more preferably 0.3 hrs, still more
preferably 0.4 hrs, and particularly preferably 0.5 hrs. On the
other hand, the upper limit of the irradiation time of the infrared
ray is preferably 20 hrs, more preferably 10 hrs, still more
preferably 5 hrs, and particularly preferably 1 hour. When the
irradiation time of the infrared ray is shorter than the lower
limit, the amount of volatilization of the polyene compounds
becomes small and thus the coloring may not be sufficiently
prevented. On the other hand, when the irradiation time is beyond
the upper limit, elevation of the resin temperature becomes
drastic, whereby deterioration of the resin is significantly
enhanced, and also handleability may be deteriorated due to
dissolution of the resin.
[0045] <Method for Producing EVOH Resin>
[0046] Hereinafter, the method for producing an EVOH resin of the
present invention is specifically explained. Specifically, the
method for producing an EVOH resin of the present invention has,
similarly to general methods for producing EVOH resins:
[0047] a polymerization step for comopolymerizing ethylene and a
vinyl ester to obtain EVAc;
[0048] a saponification step for saponifying the EVAc to obtain
EVOH;
[0049] a pelletization step for obtaining a hydrous pellet
containing EVOH from a solution containing EVOH obtained in the
saponification step;
[0050] a washing step for washing the hydrous pellet;
[0051] a drying step for drying the hydrous pellet to obtain a dry
pellet; and
[0052] a molding step for molding the dry pellet to obtain a molded
product including EVOH,
[0053] and furthermore, the aforementioned step of irradiation with
an infrared ray is included. It should be noted that steps other
than the saponification step and the step of irradiation with an
infrared ray are not prerequisite.
[0054] (Polymerization Step)
[0055] Although a copolymerization process of ethylene with the
vinyl ester is not particularly limited, for example, any of
solution polymerization, suspension polymerization, emulsion
polymerization, bulk polymerization and the like may be employed.
Also, either a continuous system or a batchwise system may be
employed.
[0056] As the vinyl ester used in polymerization, fatty acid vinyl
such as vinyl acetate, vinyl propionate or vinyl pivalate, or the
like may be suitably used.
[0057] In the polymerization described above, in addition to the
aforementioned components, a copolymerizable monomer as a
copolymerization component, for example, alkene; an unsaturated
acid such as acrylic acid, methacrylic acid, crotonic acid, maleic
acid or itaconic acid, or an anhydride, a salt, a mono- or dialkyl
ester thereof, or the like; nitrile such as acrylonitrile or
methacrylonitrile; amide such as acrylamide or methacrylamide;
olefin sulfonic acid such as vinylsulfonic acid, allylsulfonic acid
or metaallylsulfonic acid, or a salt thereof; an alkylvinyl ether,
vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene
chloride or the like may be also copolymerized in a small
amount.
[0058] Additionally, a vinylsilane compound may be included in an
amount of 0.0002% by mole or greater and 0.2% by mole or less as a
copolymerization component. Herein, the vinylsilane compound may
include, for example, vinyltrimethoxysilane, vinyltriethoxysilane,
vinyltri(.beta.-methoxy-ethoxy)silane,
.gamma.-methacryloyloxypropylmethoxysilane or the like. Of these,
vinyltrimethoxysilane, or vinyltriethoxysilane is suitably
used.
[0059] A solvent which may be used in the polymerization is not
particularly limited as long as it is an organic solvent which can
dissolve ethylene, vinyl ester and the ethylene-vinyl ester
copolymer. As such a solvent, for example, an alcohol such as
methanol, ethanol, propanol, n-butanol or tert-butanol; dimethyl
sulfoxide or the like may be used. Of these, methanol is
particularly preferred in light of ease in removal and separation
after the reaction.
[0060] As a catalyst for use in the polymerization, for example, an
azonitrile based initiator such as 2,2-azobisisobutyronitrile,
2,2-azobis-(2,4-dimethylvaleronitrile),
2,2-azobis-(4-methoxy-2,4-dimethylvaleronitrile) or
2,2-azobis-(2-cyclopropylpropionitrile); an organic peroxide based
initiator such as isobutyryl peroxide, cumyl peroxyneodecanoate,
diisopropyl peroxycarbonate, di-n-propyl peroxydicarbonate, t-butyl
peroxyneodecanoate, lauroyl peroxide, benzoyl peroxide or t-butyl
hydroperoxide, or the like may be used.
[0061] The polymerization temperature is preferably 20.degree. C.
or greater and 90.degree. C. or less, and more preferably
40.degree. C. or greater and 70.degree. C. or less. polymerization
time is preferably 2 hrs or longer and 15 hrs or shorter, and more
preferably 3 hrs or longer and 11 hrs or shorter. The rate of
polymerization is preferably no less than 10% and no greater than
90%, and more preferably no less than 30% and no greater than 80%
relative to the vinyl ester charged. The resin content in the
solution after the polymerization is preferably 5% by mass or
greater and 85% by mass or less, and more preferably 20% by mass or
greater and 70% by mass or less.
[0062] After carrying out the polymerization for a predetermined
time, or after reaching a predetermined rate of polymerization, a
polymerization inhibitor is added if necessary, and unreacted
ethylene gas is removed by evaporation, followed by removing
unreacted vinyl ester. As a process of removing an unreacted vinyl
ester, for example, a process including continuously supplying the
copolymer solution at a constant rate through an upper part of a
tower filled with Raschig ring, blowing therein an organic solvent
vapor such as methanol through a lower part of the tower,
distilling off mixed vapor of the organic solvent such as methanol
and unreacted vinyl ester through the top of the tower, and taking
out the copolymer solution from which the unreacted vinyl ester was
removed through the bottom of the tower, or the like may be
employed.
[0063] (Step of Irradiation with Infrared Ray 1: Irradiation on
EVAc)
[0064] By irradiating the ethylene-vinyl ester copolymer (EVAc)
prior to saponification obtained by the aforementioned process with
an infrared ray, an EVOH resin having sufficient long-run
workability in melt molding, and enabling prevention of coloring
such as yellowing can be finally obtained. The temperature of the
EVAc resin in irradiation with an infrared ray is preferably
40.degree. C. or greater and 110.degree. C. or less. When the
temperature of the EVAc resin falls within this range, the polyene
compounds included in the resin are volatilized, and thus
occurrence of coloring such as yellowing can be further prevented.
In this respect, the EVAc resin on which an infrared ray is
irradiated may be either a paste composed of the copolymer, or a
solution containing the copolymer.
[0065] Note that in the case in which a solution containing the
EVAc resin is employed, the temperature of the EVAc resin is equal
to the temperature of the solution. In the case of a solid such as
a paste, the temperature of the EVAc resin is determined by
measuring the temperature of the paste or the like with a
thermometer inserted into the paste every 5 min until a constant
measurement is found, and calculating an average temperature of the
measurements found at five sites.
[0066] The lower limit of the temperature of EVAc during the
irradiation with an infrared ray is preferably 40.degree. C., more
preferably 45.degree. C., still more preferably 50.degree. C., and
particularly preferably 60.degree. C. On the other hand, the upper
limit of the temperature of the copolymer is preferably 110.degree.
C., more preferably 90.degree. C., still more preferably 80.degree.
C., and particularly preferably 70.degree. C. When the temperature
of the copolymer is below the lower limit, movement of the
molecular chain of EVAc becomes insufficient, volatilization of the
polyene compounds that become the cause of coloring does not occur
sufficiently. On the other hand, when the temperature is beyond the
upper limit, deterioration of the copolymer proceeds, leading to
enhanced coloring, and thus the appearance of the resulting EVOH
resin may be finally deteriorated.
[0067] (Saponification Step)
[0068] Next, a step of saponifying EVAc is included in the present
invention. The saponification process may be either continuous
system, or a batchwise system. The catalyst which may be used in
the saponification is not particularly limited, but is preferably
an alkali catalyst, and for example, sodium hydroxide, potassium
hydroxide, alkali metal alcoholate or the like may be used.
[0069] Conditions of saponification may include, for example, in
the case of batchwise system: copolymer solution concentration
being 10% by mass or greater and 50% by mass or less; the reaction
temperature being 30.degree. C. or greater and 60.degree. C. or
less; the amount of the catalyst used being 0.02 mol or greater and
0.6 mol or less per mol of the vinyl ester structural unit; and the
saponification time being 1 hour or longer and 6 hrs or
shorter.
[0070] In this manner, a solution or a paste containing EVOH is
obtained. Since EVOH yielded after completing the saponification
reaction contains the alkali catalyst, by-product salts such as
sodium acetate and potassium acetate, and other impurities, these
are preferably removed by neutralizing and washing as needed. When
EVOH after completing the saponification reaction is washed with
water that scarcely contains metal ion, chloride ion and the like
such as ion exchanged water, sodium acetate, potassium acetate and
the like may partly remain.
[0071] (Pelletization Step)
[0072] Next, in the pelletization step, the EVOH solution obtained
as described above is pelletized by extrusion to give a strand
form. Alternatively, this solution may be pelletized by cutting in
a molten state.
[0073] When an EVOH solution is pelletized by extrusion to give a
strand form, water or a water/alcohol mixed solvent, aromatic
hydrocarbons such as benzene and acetone, ketones such as methyl
ethyl ketone, ethers such as dipropyl ether, organic acid esters
such as methyl acetate, ethyl acetate and methyl propionate, and
the like may be used as a solidification liquid for use in
deposition, but water or a water/alcohol mixed solvent is preferred
in light of easy handling. As the alcohol, methanol, ethanol,
propanol or the like may be used, and methanol is preferably used
in terms of industrial aspects. Although the mass ratio of the
solidification liquid to the strand of EVOH in the solidification
liquid (solidification liquid/strand of EVOH) is not particularly
limited, it is preferably 50 or greater and 10,000 or less, and
more preferably 100 or greater and 1,000 or less. When the mass
ratio falls within this range, to obtain a hydrous EVOH pellet
having uniform size distribution is enabled.
[0074] The temperature at which the EVOH solution is brought into
contact with the solidification liquid is preferably -10.degree. C.
or greater and 40.degree. C. or less, more preferably 0.degree. C.
or greater and 20.degree. C. or less, and particularly preferably
0.degree. C. or greater and 10.degree. C. or less. The EVOH
solution is extruded into the solidification liquid as described
above to give a strand form with a nozzle having an arbitrary form.
Although the shape of such a nozzle is not particularly limited, it
is preferably a circular cylindrical shape. Also, the length is
preferably 1 cm or greater and 100 cm or less, and more preferably
cm or greater and 30 cm or less, whereas the internal diameter is
preferably 0.1 cm or greater and cm or less, and more preferably
0.2 cm or greater and 5.0 cm or less. Thus, EVOH (solution) is
extruded to give a strand form from the nozzle. In this process,
the strand may not necessarily be single, and can be extruded to
provide arbitrary number of several strands to several hundred
strands.
[0075] Next, EVOH extruded to give a strand form is cut after
sufficiently solidified, and then pelletized followed by washing
with water. With respect to the form of such a pellet, the diameter
is preferably 1 mm or greater and 10 mm or less, and the length is
preferably 1 mm or greater and 10 mm or less (more preferably, each
being 2 mm or greater and 6 mm or less) in the case of a circular
cylinder, or the diameter is preferably 1 mm or greater and 10 mm
or less (more preferably being 2 mm or greater and 6 mm or less) in
the case of a sphere.
[0076] (Washing Step)
[0077] Subsequently, the hydrous EVOH pellet is preferably washed
with water at a temperature of 10.degree. C. or greater and
40.degree. C. or less in a water bath. Oligomers and impurities in
EVOH are removed by such a washing step with water.
[0078] (Drying Step)
[0079] Thereafter, a drying step may be included in which the
hydrous pellet is dried to obtain a dry pellet having a water
content of 0.01% by mass or greater and less than 10% by mass.
Although the drying process is not particularly limited, hot-air
drying may be exemplified.
[0080] (Molding Step)
[0081] In addition, the dried EVOH resin may be formed into any of
various types of a molded product such as a film, sheet, vessel,
pipe or fiber by melt molding. It is possible to subject these
molded articles to remolding for the purpose of reuse of the same
after crushing. Alternatively, the film, sheet, fiber or the like
can also be monoaxially or biaxially stretched.
[0082] As the melt molding process, extrusion molding, inflation
extrusion, blow molding, melt spinning, injection molding and the
like are permitted.
[0083] The melt temperature in carrying out the melt molding is not
particularly limited, but is preferably about 150.degree. C. or
greater and 300.degree. C. or less.
[0084] (Step of Irradiation with Infrared Ray 2: Irradiation on
EVOH)
[0085] Also by irradiating EVOH with an infrared ray after
subjecting to the aforementioned saponification step, an EVOH resin
having sufficient long-run workability in melt molding, and
enabling prevention of coloring such as yellowing can be finally
obtained. The resin containing EVOH irradiated with an infrared ray
may be any one of a solution, a paste, a hydrous pellet, a dry
pellet or a molded product including EVOH. The timing when the step
of irradiating with an infrared ray is carried out not particularly
limited as long as it is simultaneously with the saponification
step or following the saponification step, and the irradiation step
may be carried out, for example,
[0086] (1) simultaneously with the saponification step, or after
the saponification step and before the pelletization step,
[0087] (2) simultaneously with the pelletization step, or after the
pelletization step and before the washing step,
[0088] (3) simultaneously with the washing step, or after the
washing step and before the drying step,
[0089] (4) simultaneously with the simultaneously with the drying
step, or after the drying step and before the molding step, or
[0090] (5) simultaneously with the molding step, or after the
molding step.
[0091] Of these, carrying out the step of irradiation with an
infrared ray is carried out preferably after the pelletization
step, and specifically, carrying out after the (2) above is
preferred since the concentration of the EVOH resin is low in the
case of solution and paste forms. Since the hydrous pellets have a
so high water content that the resin temperature is not elevated
satisfactorily by irradiation with an infrared ray, whereby the
polyene compound may not be volatilized enough; therefore, the
irradiation with an infrared ray is also preferably carried out
after the drying step, and more specifically after the (4) above.
On the other hand, in the case of molded products such as films,
the water content is low, and thus azeotropy of the polyene
compound with water is less likely to occur; therefore, the
irradiation with an infrared ray is carried out preferably on a dry
pellet, and more specifically according to the (4) above. Also, in
light of effective volatilization of the polyene compound on the
surface of the final molded product and prevention of yellowing,
irradiating an infrared ray according to the (5) above is
preferred.
[0092] The lower limit of the temperature of the EVOH resin in the
irradiation with an infrared ray is preferably the glass transition
point of the EVOH, more preferably 80.degree. C., still more
preferably 100.degree. C., and particularly preferably 130.degree.
C. On the other hand, the upper limit of the resin temperature is
preferably the melting temperature of EVOH, more preferably
160.degree. C., still more preferably 155.degree. C., and
particularly preferably 150.degree. C. When the resin temperature
is below the lower limit, the stretching vibration of the hydroxyl
group included in the resin is not sufficient, and thus
volatilization of polyene does not occur enough. On the other hand,
when the resin temperature is beyond the upper limit, deterioration
of the resin proceeds, leading to enhanced coloring, and thus the
appearance may be deteriorated.
[0093] Note that in the case in which a solution containing the
EVOH resin is employed, the temperature of the EVOH resin is equal
to the temperature of the solution. In the case of a pellet or a
molded product, the temperature of the EVOH resin is determined by
measuring the temperature of the stacked pellet or the molded
product with a thermometer inserted into it every 5 min until a
constant measurement is found, and calculating an average
temperature of the measurements found at five sites.
[0094] Hereinafter, the water content of the hydrous pellet before
irradiating with an infrared ray, or that of the dry pellet will be
explained. In this process, when a pellet having a water content
before irradiating with an infrared ray of 10% by mass or greater
and 200% by mass or less is used as the hydrous pellet, and when
the water content of 0.01% by mass or greater and less than 10% by
mass, the pellet is referred to as a dry pellet.
[0095] When the irradiation of the infrared ray is carried out on a
hydrous pellet, the upper limit of the water content of the hydrous
pellet before irradiating with an infrared ray is preferably 200%
by mass, more preferably 170% by mass, still more preferably 140%
by mass, and particularly preferably 110% by mass. When the water
content of the hydrous pellet is beyond the upper limit, the resin
temperature is not sufficiently elevated by the irradiation with an
infrared ray due to too high water content, and thus the polyene
compound may not be volatilized enough. On the other hand, although
the lower limit of the water content of the hydrous pellet before
irradiating with an infrared ray is not particularly limited, when,
for example, the hydrous pellet before the drying step is
irradiated, it is preferably 10% by mass, more preferably 40% by
mass, and particularly preferably 80% by mass in terms of its step.
In addition, when the hydrous pellet is irradiated with an infrared
ray, for example, simultaneously with the drying step, water
content of the hydrous pellet subjected to the drying step
preferably falls within the range that is the same as the water
content of the hydrous pellet before irradiating with an infrared
ray, and preferably 0.01% by mass or greater and less than 10% by
mass of the water content of the dry pellet after the drying step.
On the other hand, although the lower limit of the water content of
the hydrous pellet before irradiating with an infrared ray is not
particularly limited, when, for example, the hydrous pellet before
the drying step is irradiated, it is preferably 10% by mass, more
preferably 40% by mass, and particularly preferably 80% by mass in
terms of its step. In addition, when the hydrous pellet is
irradiated with an infrared ray, for example, simultaneously with
the drying step, water content of the hydrous pellet subjected to
the drying step preferably falls within the range that is the same
as the water content of the hydrous pellet before irradiating with
an infrared ray, and preferably 0.01% by mass or greater and less
than 10% by mass of the water content of the dry pellet after the
drying step.
[0096] Moreover, the lower limit of the water content of the dry
pellet and the molded product before irradiating with an infrared
ray is preferably 0.01% by mass, more preferably 0.02% by mass,
still more preferably 0.03% by mass, and particularly preferably
0.05% by mass. When the water content of the dry pellet and the
film or the like that is a molded product is below the lower limit,
volatilization by way of azeotropy of the polyene compound with
water does not sufficiently occur due to the too low water content.
On the other hand, although the upper limit of the water content of
the dry pellet and the molded product before irradiating with an
infrared ray is not particularly limited, it is preferably 9% by
mass, more preferably 1% by mass, and particularly preferably 0.5%
by mass in terms of its step.
[0097] It should be noted that the water content value (% by mass)
is on dry basis unless otherwise stated in particular. The water
content on dry basis is a value derived by dividing the mass of
water included in a hydrous or dry pellet by the dry mass of the
resin included in the hydrous or dry pellet. Also with respect to
molded products such as films may be similar determination can be
carried out.
[0098] <EVOH Resin>
[0099] The EVOH resin of the present invention is obtained by the
aforementioned method for production. EVOH in this EVOH resin is a
polymer having an ethylene unit and a vinyl alcohol unit as main
structural units.
[0100] The lower limit of the ethylene content of EVOH (i.e., rate
of the number of ethylene units relative to the total number of
monomer units in EVOH) is preferably 20% by mole, more preferably
25% by mole, and still more preferably 30% by mole. On the other
hand, the upper limit of the ethylene content in EVOH is preferably
60% by mole, more preferably 55% by mole, still more preferably 50%
by mole, and particularly preferably 45% by mole. When the ethylene
content of EVOH falls within this range, sufficient appearance
characteristics and long-run workability can be achieved. When the
ethylene content in EVOH is below the lower limit, for example,
water resistance, hot water resistance and gas barrier properties
under high humidity achieved upon molding a laminate may be
deteriorated, or deterioration of melt formability, occurrence of
yellowing and the like may be caused. To the contrary, when the
ethylene content of EVOH is beyond the upper limit, deterioration
of gas barrier properties achieved upon molding a laminate, and
occurrence of yellowing and the like may be likely to be
caused.
[0101] The lower limit of the degree of saponification of EVOH
(i.e., rate of the number of vinyl alcohol units relative to the
total number of vinyl alcohol units and vinyl ester units in EVOH)
is preferably 90% by mole, more preferably 95% by mole, and
particularly preferably 99% by mole. On the other hand, the upper
limit of the degree of saponification of EVOH is preferably 100% by
mole, and still more preferably 99.99% by mole. When the degree of
saponification of EVOH is below the lower limit, gas barrier
properties achieved upon molding a laminate may be deteriorated,
and coloring resistance may be unsatisfactory.
[0102] In the case in which EVOH is constituted with a mixture of
two or more kinds of EVOHs having different ethylene contents, the
ethylene content is defined as an average value calculated from the
mixed mass ratio. In this case, it is preferred that the maximum
difference between ethylene contents of two EVOHs is 30% by mole or
less, and the difference between degrees of saponification is
preferably 10% by mole or less. When carried out under conditions
out of these requirements, gas barrier properties achieved upon
molding a laminate may be deteriorated. The difference in ethylene
contents is more suitably 20% by mole or less, and more suitably
15% by mole or less. Also, the difference in the degrees of
saponification is more suitably no greater than 7%, and still more
suitably no greater than 5%.
[0103] The EVOH resin of the present invention achieves
advantageous effects of the present invention by volatilization the
polyene compounds that become the cause of coloring owing to the
irradiation with an infrared ray as described above, the EVOH resin
preferably does not substantially contain a polyene compound in a
region from the surface over the depth of 5 nm. In this regard, the
phrase "does not substantially contain a polyene compound"
indicates that when the surface of the EVOH resin is analyzed using
"TOF-SIMS 5" manufactured by ION-TOF GmbH, peak intensity of
polyene compounds is tenth or less as compared with the peak
intensity of the infrared ray-unirradiated EVOH resin. Note that
the aforementioned definition has substantially the same meaning
that the content of a polyene compound on the surface of the EVOH
resin is tenth or less of the content of the polyene compound
inside the EVOH resin when the EVOH resin has a solid form.
[0104] Measurement Conditions
[0105] Name of apparatus: manufactured by ION-TOF GmbH "TOF-SIMS
5"
[0106] Primary ion gun: Bi.sub.3.sup.++ ion gun,
[0107] Pulse electric current value: 0.2 pA
[0108] Applied voltage: 25 keV
[0109] Frequency: 10 kHz
[0110] Measurement mode: bunching mode
[0111] Charge correction: electron gun used
[0112] Measurement range: 75.times.75 .mu.m (128.times.128
pixel)
[0113] Number of scanning time: 32 (within static limit range)
[0114] Polarity: cation detected
[0115] (Additives)
[0116] In order to improve each performance, the EVOH resin
obtained by the method for production of the present invention
preferably contains a variety of additives such as acid, metal
salts, etc. The additives may include alkali metal salts,
carboxylic acids and/or carboxylate ions, phosphate compounds and
boron compounds described later. According to the method for
production of the present invention, occurrence of yellowing and
the like can be prevented also when these additives are contained
in the resin.
[0117] The EVOH resin of the present invention preferably contains
an alkali metal ion in light of thermal stability. The content of
the alkali metal ion in dry EVOH resin is preferably 2.5 .mu.mol/g
or greater and 22 .mu.mol/g or less, more preferably 3.5 .mu.mol/g
or greater and 16 .mu.mol/g or less, and particularly preferably
4.5 .mu.mol/g or greater and 10 .mu.mol/g or less in alkali metal
element equivalent.
[0118] The process for adjusting the content of the alkali metal
element to fall within the above range is not particularly limited.
Note that EVOH after subjecting to the saponification reaction
usually contains the alkali metal element as a saponification
catalyst residue. Thus, a process in which EVOH after subjecting to
the saponification reaction using the aforementioned process is
washed thereby removing the alkali metal element, and thereafter
the alkali metal element is included in a given amount again to
obtain an EVOH resin is preferred.
[0119] The process for including the alkali metal element in the
EVOH resin may include: a process of immersing EVOH in a solution
containing an alkali metal element; a process of the EVOH resin is
melted and mixed with a solution containing a compound including an
alkali metal element, or an alkali metal element, a process of
dissolving the EVOH resin in a suitable solvent and mixed with a
compound including an alkali metal element; and the like.
[0120] In the case in which the EVOH resin is immersed in a
solution containing an alkali metal element, the concentration of
the alkali metal element in this solution is not particularly
limited. Also, the solvent of the solution is not particularly
limited, but is preferably an aqueous solution in light of the
handleability and the like. The mass of the solution used for
immersing the EVOH resin is usually at least three times, and
preferably at least 10 times the mass of EVOH as dried. Although
suitable range of the immersion time may vary depending on the form
of the EVOH resin, it is usually 1 hour or longer, and preferably 2
hrs or longer. The mode of the immersion in the solution is not
particularly limited, and the immersion may be carried out after
dividing into a plurality of aliquots, or the immersion may be
carried out once. In light of simplification of the step, the
immersion is preferably carried out once. A tower system apparatus
may be suitably used to continuously carry out the immersion.
[0121] The EVOH resin of the present invention may also contain a
carboxylic acid and/or a carboxylate ion. The content of the
carboxylic acid and/or the carboxylate ion in the dry EVOH resin is
preferably 0.05 .mu.mol/g or greater and 25 .mu.mol/g or less, more
preferably 0.5 .mu.mol/g or greater and 22 .mu.mol/g or less, still
more preferably 2 .mu.mol/g or greater and 20 .mu.mol/g or less,
and particularly preferably 5 .mu.mol/g or greater and 18 .mu.mol/g
or less. Examples of the carboxylic acid include succinic acid,
adipic acid, benzoic acid, capric acid, lauric acid, glycolic acid,
lactic acid, formic acid, acetic acid, propionic acid and the like.
Of these, acetic acid, propionic acid and lactic acid are more
preferred, and acetic acid and propionic acid are particularly
preferred, in light of appropriate acidity, and ease in controlling
the pH of the EVOH resin. Anions of these carboxylic acids are
included in preferable carboxylate ions. When the content of the
carboxylic acid and/or the carboxylate ion exceeds 25 .mu.mol/g,
thermal stability of the EVOH resin is deteriorated, and the
resulting resin or molded article is likely to be accompanied by
poor appearance such as coloring, fish eye, streak and the
like.
[0122] Moreover, the EVOH resin of the present invention preferably
contains a phosphate compound in an amount of 1 to 500 ppm in
phosphate equivalent. The type of the phosphate compound is not
particularly limited, and any of various types of acids such as
phosphoric acid and phosphorous acid, and salts thereof may be
used. The phosphate may be any one of primary phosphate, secondary
phosphate and tertiary phosphate, Also, the cation species is not
particularly limited; however, it is preferably an alkali metal
salt, or an alkaline earth metal salt. In particular, the phosphate
compound is preferably included in the form of phosphoric acid,
sodium dihydrogen phosphate, potassium dihydrogen phosphate,
disodium hydrogen phosphate or dipotassium hydrogen phosphate, and
adding the phosphate compound in the form of phosphoric acid,
sodium dihydrogen phosphate or potassium dihydrogen phosphate is
more preferred.
[0123] Furthermore, the upper limit of the content of the phosphate
compound is preferably 400 ppm or less, and more preferably 300 ppm
or less in phosphate equivalent. Also, the lower limit of the
content of the phosphate compound is more preferably 3 ppm or
greater, still more preferably 5 ppm or greater, and particularly
preferably 10 ppm or greater.
[0124] In addition, the EVOH resin may contain a boron compound in
the range not to impair the object of the present invention.
Examples of the boron compound include boric acids such as
orthoboric acid, metaboric acid, and tetraboric acid; boric acid
esters, boric acid salts, hydrogenated boron compounds, and the
like. Examples of the boric acid salt include borax, and alkali
metal salts and alkaline earth metal salts of the aforementioned
various types of boric acids, and the like. Among these compounds,
orthoboric acid is preferred. When a boron compound is added, the
content in terms of boron element is preferably in the range of 20
to 2000 ppm, and more preferably in the range of 50 to 1800
ppm.
[0125] As described in the foregoing, the EVOH resin obtained by
the method for production of the present invention may contain at
least one selected from the group consisting of carboxylic acid,
phosphate compounds and boron compound as needed, and the process
for including the same is not particularly limited. For example, a
process that is similar to the process for including the
aforementioned alkali metal element may be employed.
[0126] (Other Additives, etc.)
[0127] To the EVOH resin obtained by the method for production of
the present invention may be also added in addition to the
aforementioned additives, an appropriate amount of a plasticizer, a
stabilizer, a surfactant, a coloring agent, an ultraviolet ray
absorbing agent, a slip agent, an antistatic agent, a desiccating
agent, a crosslinking agent, a metal salt other than alkali metals,
a filler, a reinforcing agent such as various types of fiber, and
the like in the range not to impair the effects of the present
invention.
[0128] Furthermore, an appropriate amount of a thermoplastic resin
other than EVOH may be also blended in the range not to impair the
effects of the present invention. Examples of the thermoplastic
resin which may be used include various types of polyolefins
(polyethylene, polypropylene, poly 1-butene, poly
4-methyl-1-pentene, ethylene-propylene copolymers, copolymers of
ethylene with .alpha.-olefin having 4 or more carbon atoms,
copolymers of polyolefin and maleic anhydride, ethylene-vinyl ester
copolymers, ethylene-acrylate copolymer, or modified polyolefins
prepared by grafting modification of the same with an unsaturated
carboxylic acid or a derivative thereof), various types of nylon
(nylon-6, nylon-6,6, nylon-6/6,6 copolymer, etc.), polyvinyl
chloride, polyvinylidene chloride, polyesters, polystyrene,
polyacrylonitrile, polyurethane, polyacetal and modified polyvinyl
alcohol resins, and the like.
[0129] Although the form of the EVOH resin of the present invention
is not particularly limited, any one of molded product forms such
as a solution form, a paste form, a powder form, a pellet form and
a film form is acceptable. The EVOH resin is preferably in a pellet
form or a film form owing to easily executed irradiation with an
infrared ray, and easily achievable effect of preventing yellowing
by way of the irradiation.
[0130] (Laminate)
[0131] The laminate of the present invention is a laminate provided
with at least one layer obtained from the EVOH resin of the present
invention. The layer structure of the laminate is not particularly
limited; however, provided that: a layer obtained from the resin of
the present invention is designated as E; a layer obtained from an
adhesive resin is designated as Ad; and a layer obtained from a
thermoplastic resin is designated as T, examples of the layer
structure include T/E/T, E/Ad/T, T/Ad/E/Ad/T, and the like. Each
layer of these may be either monolayer, or a multilayer.
[0132] The method for producing the laminate is not particularly
limited. For example, a method of melt extruding a thermoplastic
resin onto a molded product obtained from the EVOH resin of the
present invention (film, sheet. Etc.); a method of coextruding the
EVOH resin of the present invention and other thermoplastic resin;
a method of coinjecting the EVOH resin of the present invention
with a thermoplastic resin; a method of laminating a molded article
formed from the EVOH resin of the present invention and a film or a
sheet of other base material using a well-known adhesive such as an
organic titanium compound, an isocyanate compound or a polyester
based compound; and the like may be exemplified.
[0133] Among these methods, a method of coextruding the EVOH resin
of the present invention and other thermoplastic resin is
preferably used. The EVOH resin of the present invention is
superior in long-run workability and appearance characteristics,
and in particular, coloring is less likely to occur even if melted
at a comparatively high temperature. Therefore, even if the EVOH
resin of the present invention and other thermoplastic resin having
a comparatively high melting temperature are coextruded, a laminate
being accompanied by suppressed occurrence of coloring such as
yellowing, and being superior in the appearance can be
obtained.
[0134] Examples of the thermoplastic resin used for other layer in
the laminate include: homopolymers of an olefin or copolymers
thereof such as linear low density polyethylene, low density
polyethylene, medium density polyethylene, high density
polyethylene, ethylene-vinyl acetate copolymers, ethylene-propylene
copolymers, polypropylene, and propylene-.alpha.-olefin copolymers
(.alpha.-olefin having 4 to 20 carbon atoms), polybutene,
polypentene; polyesters such as polyethylene terephthalate;
polyamides such as polyester elastomers, nylon-6, and nylon-6,6;
polystyrene, polyvinyl chloride, polyvinylidene chloride, acrylic
resins, vinyl ester based resins, polyurethane elastomers,
polycarbonate, chlorinated polyethylene, chlorinated polypropylene,
and the like. Of these, polypropylene, polyethylene,
ethylene-propylene copolymers, ethylene-vinyl acetate copolymers,
polyamides, polystyrene, polyesters are preferably used.
[0135] The aforementioned adhesive resin is not particularly
limited as long as it has adhesiveness with the EVOH resin of the
present invention and the thermoplastic resin, but adhesive resins
containing a carboxylic acid modified polyolefin are preferred. As
the carboxylic acid modified polyolefin, a carboxyl
group-containing modified olefin-derived polymer can be suitably
used which is obtained by allowing an ethylenic unsaturated
carboxylic acid or an anhydride thereof to be chemically bonded
(for example, addition reaction, graft reaction, etc.) to an
olefin-derived polymer. In this regard, examples of the
olefin-derived polymer include, e.g., polyolefins such as
polyethylene (low pressure, middle pressure, high pressure), linear
low density polyethylene, polypropylene and polybutene, copolymers
(for example, ethylene-vinyl acetate copolymers, ethylene-ethyl
acrylate copolymers, etc.) of olefin and other monomer (vinyl
ester, unsaturated carboxylate ester, etc.). Among these, linear
low density polyethylene, ethylene-vinyl acetate copolymers
(content of vinyl acetate being 5% by mass or greater and 55% by
mass or less) and ethylene-ethyl acrylate copolymers (content of
ethyl acrylate being 8% by mass or greater and 35% by mass or less)
are preferred, and linear low density polyethylene and
ethylene-vinyl acetate copolymers are particularly preferred. As
the ethylenic unsaturated carboxylic acid or an anhydride thereof,
ethylenic unsaturated monocarboxylic acids, or esters thereof,
ethylenic unsaturated dicarboxylic acids, or mono- or diesters
thereof, or anhydrides of the same are exemplified, and of these,
ethylenic unsaturated dicarboxylic acid anhydrides are preferred.
Specifically, maleic acid, fumaric acid, itaconic acid, maleic
anhydride, itaconic anhydride, maleic monomethyl ester, maleic
monoethyl ester, maleic diethyl ester, fumaric monomethyl ester and
the like are included, and particularly, maleic anhydride is
suitable.
[0136] Although the process for coextrusion of the EVOH resin of
the present invention and the thermoplastic resin, etc., is not
particularly limited, a multimanifold-merging T die method, a
feedblock-merging T die method, an inflation method, and the like
may be exemplified.
[0137] By subjecting thus obtained coextrusion laminate to
secondary processing, various types of molded products (films,
sheets, tubes, bottles, etc.) can be obtained. The various types of
molded products include, for example, articles as in the
following:
[0138] (1) multilayer costretched sheets or films obtained by
stretching a laminate (sheet or film, etc.) in an uniaxial or
biaxial direction, followed by subjecting to a heat treatment;
[0139] (2) multilayer rolled sheets or films obtained by rolling a
laminate (sheet or film, etc.);
[0140] (3) multilayer tray cup shaped vessels obtained by
subjecting a laminate (sheet or film, etc.) to a hot forming
process such as vacuum forming, air-pressure forming or vacuum
air-pressure forming; and
[0141] (4) bottles, cup shaped vessels and the like obtained by
stretch blow molding or the like of a laminate (pipe, etc.).
[0142] Note that the secondary processing is not limited to each
process illustrated for obtaining the molded product described
above, and for example, any well-known secondary processing other
than the aforementioned processes such as blow molding may be used
ad libitum.
[0143] Since the laminate has a layer obtained from an EVOH resin
having appearance characteristics (noncoloring properties) and
sufficient long-run workability, it is accompanied by fewer fish
eye, gel and seed (dirt under paint) and less coloring such as
yellowing and thus, for example, can be suitably used as a food
vessel and the like such as a deep draw vessel, a cup shape vessel,
and a bottle.
EXAMPLES
[0144] Hereinafter, the present invention is explained in more
detail by way of Example, but the present invention is not in any
way limited to these Examples.
[0145] (Quantitative Determination Method)
[0146] It should be noted that each quantitative determination in
Examples herein was carried out according to the following
method.
[0147] (1) Ethylene Content of EVOH
[0148] The ethylene content of an ethylene-vinyl alcohol copolymer
was determined according to the analysis method described below by
carrying out .sup.1H-NMR measurement under the following
measurement conditions.
[0149] Measurement Conditions [0150] Name of apparatus:
manufactured by JEOL Ltd., NMR spectrometer "Lambda 500" [0151]
Observation frequency: 500 MHz [0152] Solvent: DMSO-d6 [0153]
Polymer concentration: 4% by mass [0154] Measurement temperature:
80.degree. C. [0155] Cumulated number: 256 times
[0156] Analysis Method
[0157] The ethylene content was calculated from the intensity ratio
of: methine protons of ethylene units, vinyl alcohol units and
vinyl ester units (peak at 0.6 to 2.1 ppm), methine protons of
vinyl alcohol units (peak at 3.15 to 4.15 ppm), and methine protons
of vinyl ester units (peak at 1.95 to 2.00 ppm).
[0158] (2) Degree of Saponification
[0159] Dry EVOH pellet was crushed by freeze crushing. Thus
resulting crushed EVOH was sieved with a sieve having a nominal
dimension of 1 mm (according to normal sieve standard JIS-Z8801).
EVOH powder passed through the sieve in an amount of 5 g was
immersed in 100 g of ion exchanged water, and the mixture was
stirred at 85.degree. C. for 4 hrs, followed by an operation of
drainage and drying repeated twice. Using thus obtained powder EVOH
after washing, measurement of .sup.1H-NMR was carried out under the
following measurement conditions, and the degree of saponification
was determined by the analysis method described below.
[0160] Measurement Conditions [0161] Name of apparatus:
manufactured by JEOL Ltd., [0162] NMR spectrometer "Lambda 500"
[0163] Observation frequency: 500 MHz [0164] Solvent: DMSO-d6
[0165] Polymer concentration: 4% by mass [0166] Measurement
temperature: 40.degree. C. and 95.degree. C. [0167] Cumulated
number: 600 times [0168] Pulse delay time: 3.836 sec [0169] Sample
rotation speed: 10 to 12 Hz [0170] Pulse width (90.degree. pulse):
6.75 .mu.sec
[0171] Analysis Method
[0172] By the measurement at 40.degree. C., a peak of hydrogen in
water molecules was found at around 3.3 ppm, which overlapped with
a peak in the range of 3.1 to 3.7 ppm among peaks of methine
hydrogen of the vinyl alcohol units of EVOH. On the other hand,
when measured at 95.degree. C., the overlapping caused at
40.degree. C. could be obviated; however, a peak of hydrogen of the
hydroxyl groups of the vinyl alcohol units of EVOH was present at
around 4 to 4.5 ppm, which overlapped with the range of 3.7 to 4
ppm of peaks of methine hydrogen of vinyl alcohol units of EVOH.
Accordingly, for quantitative determination of methine hydrogen of
vinyl alcohol units of EVOH (3.1 to 4 ppm), measurement data at
95.degree. C. were employed with respect to the range of 3.1 to 3.7
ppm, and measurement data at 40.degree. C. were employed with
respect to the range of 3.7 to ppm in order to avoid overlapping
with peaks of hydrogen of water or hydroxyl groups. Thus, the total
amount of the methine hydrogen was quantitatively determined in
terms of the total value of these measurements. Note that the peak
of hydrogen of water or hydroxyl group has been known to shift to a
high magnetic field side by elevating the measurement temperature.
Therefore, analyses were conducted as in the following using both
measurement results at 40.degree. C. and 95.degree. C. From the
spectrum obtained at 40.degree. C. as described above, an
integrated value (I.sub.1) of the peak of the chemical shift at 3.7
to 4 ppm, and an integrated value (I.sub.2) of the peak of the
chemical shift at 0.6 to 1.8 ppm were determined. On the other
hand, from the spectrum obtained at 95.degree. C., an integrated
value (I.sub.3) of the peak of the chemical shift at 3.1 to 3.7
ppm, an integrated value (I.sub.4) of the peak of the chemical
shift at 0.6 to 1.8 ppm, and an integrated value (I.sub.5) of the
peak of the chemical shift at 1.9 to 2.1 ppm were determined. In
this process, the peak of the chemical shift at 0.6 to 1.8 ppm
principally derives from methylene hydrogen, whereas the peak of
the chemical shift at 1.9 to 2.1 ppm derives from methyl hydrogen
in unsaponified vinyl acetate units. From these integrated values,
a degree of saponification was calculated according to the
following formula (II).
[ formula 2 ] Degree of saponification ( mol % ) = ( I 1 / I 2 + I
3 / I 4 ) .times. 100 ( I 1 / I 2 + I 3 / I 4 ) + ( I 5 / I 4 ) / 3
( II ) ##EQU00002##
[0173] (3) Melting Temperature of EVOH
[0174] The melting temperature of EVOH was determined by a
differential scanning calorimetric analysis. More specifically, a
differential scanning calorimetric analysis (manufactured by Seiko
Electronics Co., Ltd., differential scanning calorimeter (DSC)
model RDC220/SSC5200H) was performed on the pellet of the EVOH
resin according to JIS-K7121 by elevating the temperature from
30.degree. C. to 220.degree. C. at a rate of 10.degree. C./min,
followed by quenching at a rate of 100.degree. C./min to 30.degree.
C. and again elevating the temperature from 30.degree. C. to
220.degree. C. at a rate of 10.degree. C./min. For calibration of
the temperature, indium and lead were used. A peak melting
temperature (Tpm) was determined from the second run chart as
referred to in the JIS described above, and defined as the melting
temperature.
[0175] (4) Water Content of EVOH Resin Pellet
[0176] Using a halogen moisture analyzer "HR73" manufactured by
Mettler-Toledo International Inc., the water content of the EVOH
pellet on dry basis was measured under conditions of a drying
temperature of 180.degree. C., a drying time of 20 min, and a
sample amount of about 10 g.
[0177] (5) Quantitative Determination of Alkali Metal Ion
[0178] The dry EVOH pellet was crushed by freeze crushing. Thus
obtained EVOH powder in an amount of 10 g and 50 mL of ion
exchanged water were charged in a 100 mL stoppered Erlenmeyer flask
equipped with a cooling condenser, and the mixture was stirred at
95.degree. C. for 10 hrs to execute heat extraction. Thus obtained
extract in a volume of 2 mL was diluted with 8 mL of ion exchanged
water. Thus diluted extract was subjected to a quantitative
analysis using an ICP emission spectrophotometer "Optima 4300 DV"
manufactured by PerkinElmer Japan Co., Ltd., at an observation
wavelength of 589.592 nm, whereby the amount of sodium ion was
quantitatively determined.
[0179] (6) Quantitative Determination of Phosphate Compounds
[0180] The dry EVOH pellet was crushed by freeze crushing. Thus
obtained EVOH powder in an amount of 1.0 g, 15 mL of conc. nitric
acid and 4 mL of conc. sulfuric acid were charged into a stoppered
100 mL Erlenmeyer flask equipped with a cooling condenser to
execute heat degradation at 200 to 230.degree. C. Thus obtained
solution was diluted to 50 mL with ion exchanged water in a
volumetric flask. The solution was subjected to a quantitative
analysis using an ICP emission spectrophotometer "Optima 4300 DV"
manufactured by PerkinElmer Japan Co., Ltd., at an observation
wavelength of 214.914 nm, whereby the amount of phosphorus element
was quantitatively determined, and the amount of phosphate
compounds was calculated to give a value of phosphate
equivalent.
[0181] (7) Quantitative Determination of Boron Compound
[0182] A dry EVOH pellet provided as a sample in an amount of 50 mg
was completely combusted by an oxygen flask combustion method, and
thus resultant combusted ash deposition was dissolved in 10 mL of a
1 mol/L aqueous nitric acid solution. The solution was subjected to
a quantitative analysis using an ICP emission spectrophotometer
"Optima 4300 DV" manufactured by PerkinElmer Japan Co., Ltd., at an
observation wavelength of 249.667 nm, whereby the content of boron
compounds was obtained in a value of boron element equivalent.
[0183] (8) Intensity of the Infrared Ray
[0184] The intensity of the infrared ray was calculated by a
measuring method illustrated in the foregoing embodiments.
[0185] (9) Resin Temperature in the Step of Irradiation with
Infrared Ray
[0186] The temperature of the EVAc resin paste was measured with a
thermometer in terms of the temperature of this paste. Also, the
temperature of the EVOH resin was measured by a method illustrated
in the foregoing embodiments.
Example 1
Production of Ethylene-Vinyl Acetate Copolymer
[0187] To a 250 L pressure reactor equipped with a stirrer, a
nitrogen feed port, an ethylene feed port, an initiator addition
port and a delay (consecutive addition) solution addition port were
charged 83.0 kg of vinyl acetate and 26.6 kg of methanol, and the
temperature was elevated to 60.degree. C. Thereafter, the system
was substituted with nitrogen by nitrogen bubbling for 30 min.
Next, ethylene was charged such that the reactor pressure became
3.6 MPa. As an initiator a 2.5 g/L solution of
2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (AMV) dissolved in
methanol was prepared, and the solution was substituted with
nitrogen by bubbling nitrogen gas. After the internal temperature
of the polymerization bath was adjusted to 60.degree. C., 362 mL of
the initiator solution was injected to initiate polymerization.
During the polymerization, ethylene was introduced to maintain the
reactor pressure of 3.6 MPa and the polymerization temperature of
60.degree. C., and the initiation solution was continuously added
at 1119.5 mL/hr using the aforementioned initiator solution to
perform polymerization. 5.0 hrs later, the polymerization was
stopped by cooling when the rate of polymerization reached 40%.
After the reactor was opened to remove ethylene, nitrogen gas was
bubbled to completely eliminate ethylene. Next, the copolymer
solution was continuously supplied through an upper part of a tower
filled with Raschig ring, and methanol was blown through a lower
part of the tower. Mixed vapor of methanol and unreacted vinyl
acetate monomer was allowed to outflow through the top of the
tower, whereby unreacted vinyl acetate monomer was removed through
the bottom of the tower to give a methanol solution of an
ethylene-vinyl acetate copolymer (EVAc).
[0188] (Saponification)
[0189] To thus obtained EVAc solution was added methanol to adjust
a concentration of 15% by mass. To 253.4 kg of thus prepared
methanol solution of EVAc (38 kg of EVAc in the solution) was added
76.5 L of an alkali solution (20% by mass NaOH solution in
methanol, molar ratio (MR) relative to vinyl acetate units in EVAc:
0.4) and the mixture was stirred at 60.degree. C. for 4 hrs to
carry out saponification of EVAc. After 6 hrs from starting the
reaction, the reaction liquid was neutralized by adding 11.0 kg of
acetic acid and 60 L of water to terminate the reaction.
[0190] (Washing)
[0191] The neutralized reaction liquid was transferred from the
reactor to a metal drum, and left to stand at room temperature for
16 hrs, thereby permitting cooling and hardening to give a paste
form. Thereafter, liquid was removed from the resin in the paste
form using a centrifugal separator ("H-130" manufactured by Kokusan
Centrifuge Co., Ltd., number of revolution: 1,200 rpm). Next, a
step of washing the resin with water was conducted for 10 hrs in
which washing was carried out while continuously supplying ion
exchanged water to the central portion of the centrifugal separator
from above. The conductivity of the washing liquid after 10 hrs
from starting washing was 30 .mu.S/cm (measured with "CM-30ET"
manufactured by TOA Electronics Ltd.).
[0192] (Deposition)
[0193] EVOH in the paste form obtained in this manner was dried
using a dryer at 60.degree. C. for 48 hrs to give EVOH in the form
of powder. Thus dried EVOH in the form of powder in an amount of 20
kg was dissolved in 43 L of a water/methanol mixed solution (mass
ratio: water/methanol=4/6) while stirring at 80.degree. C. for 12
hrs. Next, the stirring was stopped, and the temperature of the
dissolver was lowered to 65.degree. C. After leaving to stand for 5
hrs, degassing of the water/methanol solution of EVOH was carried
out. Then, the EVOH was extruded from a gold plate provided with a
circular opening having a diameter of 3.5 mm into a water/methanol
mixed solution (mass ratio: water/methanol=9/1) at 5.degree. C. to
allow for deposition to give a strand form, and cut to obtain a
hydrous EVOH pellet having a diameter of about 4 mm and a length of
about 5 mm.
[0194] (Washing)
[0195] Thus obtained hydrous EVOH pellet in an amount of 40 kg and
150 L of ion exchanged water were placed in a metal drum having a
height of 900 mm and an opening diameter of 600 mm. An operation of
washing at 25.degree. C. for 2 hrs while stirring, and eliminating
the liquid was repeated twice. Next, 150 L of 1 g/L aqueous acetic
acid solution was added to 30 kg of the hydrous EVOH pellet, and an
operation of washing at 25.degree. C. for 2 hrs while stirring, and
eliminating the liquid was repeated twice. Furthermore, 150 L of
ion exchanged water was added to 30 kg of the hydrous EVOH pellet,
and an operation of washing at 25.degree. C. for 2 hrs while
stirring, and eliminating the liquid was repeated six times. The
conductivity of the washing liquid after carrying out the sixth
washing was measured with "CM-30ET" manufactured by TOA Electronics
Ltd., and as a result, the washing liquid was revealed to have a
conductivity of 3 .mu.S/cm. Thus resulting hydrous EVOH pellet had
a water content of 110% by mass.
[0196] (Preparation of Each Component and Drying)
[0197] Subsequently, 3.0 kg of the hydrous EVOH pellet was charged
into 30 L of an aqueous solution for acid treatment prepared by
blending 0.80 g/L acetic acid as a carboxylic acid, 0.50 g/L sodium
acetate as an alkali metal salt, 0.015 g/L phosphoric acid as a
phosphate compound, and 0.2 g/L boric acid as a boron compound in
water at each blend rate. Immersion and stirring of the mixture
were then allowed at 25.degree. C. for about 5 hrs. The hydrous
pellet after the treatment was dried at 80.degree. C. for 3 hrs,
and subsequently at 120.degree. C. for 24 hrs to obtain an EVOH
pellet.
[0198] (EVOH Pellet)
[0199] EVOH in the EVOH pellet had an ethylene content of 32% by
mole, and a degree of saponification of 99.98% by mole or greater.
Also, the content of carboxylic acid and carboxylate ion in the
EVOH pellet was 16.7 .mu.mol/g; the content of alkali metal ion was
7.39 .mu.mol/g; the content of phosphate compounds was 10 ppm in
phosphate equivalent; and the content of boron compounds was 890
ppm in a value of boron element equivalent. This EVOH pellet had a
water content of 0.3% by mass. Also, the EVOH pellet had MFR (melt
flow rate: 210.degree. C.; load: 2160 g) of 3.6 g/10 min.
[0200] (Irradiation with Infrared Ray)
[0201] The EVOH pellet was placed into a cylindrical vessel. The
EVOH pellet was irradiated with an infrared ray from above using an
Infrared Moisture Balance "MB-30" manufactured by CBC Co., Ltd. for
1 hour, to obtain an EVOH pellet, in which coloring such as
yellowing was prevented, as an EVOH resin of Example 1. The
temperature of the EVOH pellet that is a resin temperature during
the irradiation with an infrared ray was from 130.degree. C. to
150.degree. C.
Examples 2 to 7
[0202] EVOH pellets of Examples 2 to 7 were obtained in a similar
manner to Example 1 except that the resin temperature of the EVOH
pellet during the irradiation and the intensity of the irradiation
with an infrared ray were as shown in Table 1.
Examples 8 to 11
[0203] EVOH pellets of Examples 8 to 11 were obtained in a similar
manner to Example 1 except that the resin temperature of the EVOH
pellet during the irradiation with an infrared ray, and irradiation
time of the infrared ray were as shown in Table 1.
Example 12
[0204] The water content of the EVOH pellet after preparing each
component in Example 1 and before drying was adjusted to 10% by
mass, and irradiation of the EVOH pellet with an infrared ray was
carried out by a similar method to Example 1. Subsequently, an EVOH
pellet was obtained by drying with a similar method to Example
1.
Examples 13 to 15
[0205] The hydrous EVOH pellet having a water content of 110% by
mass in Example 1 was irradiated with an infrared ray for each
irradiation time changed as shown in Table 1. Subsequently, EVOH
pellets were obtained by preparing each component and drying
according to a similar method to Example 1.
Example 16
[0206] The EVOH pellet obtained by a similar method to Example 1
was subjected to monolayer film formation under the following
conditions using a 20 mm Extruder "D2020" (D (mm)=20, L/D=20,
compression ratio=2.0, screw: full flight) manufactured by Toyo
Seiki Seisaku-sho, Ltd. to obtain an EVOH monolayer film. [0207]
Extrusion temperature: supply part/compression part/metering
part/die=180/210/220/220.degree. C. [0208] Number of revolution of
screw: 80 rpm [0209] Discharge rate: 1.0 kg/hr [0210] Drawing roll
temperature: 80.degree. C. [0211] Drawing roll speed: 3.1 m/min.
[0212] Film thickness: 50 .mu.m
[0213] Subsequently, the EVOH film was irradiated with an infrared
ray with an apparatus similar to Example 1 for 1 hour to obtain an
EVOH film, in which coloring such as yellowing was prevented, as an
EVOH resin of Example 16. The temperature of the EVOH film during
irradiation with an infrared ray was from 130.degree. C. to
150.degree. C.
Example 17
[0214] A paste composed of a methanol solution of the
ethylene-vinyl acetate copolymer in Example 1 was irradiated with
an infrared ray for 1 hour in a similar manner to Example 1. The
temperature of the EVOH paste that is a resin temperature during
irradiation with an infrared ray was from 60.degree. C. to
80.degree. C. Subsequently, as an EVOH resin of Example 17 an EVOH
pellet enabling prevention of coloring such as yellowing was
obtained by subjecting the EVOH paste to similar steps to Example
1.
Examples 18 to 19
[0215] EVOH pellets of Examples 18 and 19 were obtained in a
similar manner to Example 1 except that ethylene contents of the
EVOH were as shown in Table 1.
Comparative Example 1
[0216] An EVOH pellet of Comparative Example 1 was obtained in a
similar manner to Example 1 except that the EVOH pellet was not
irradiated with an infrared ray.
Comparative Example 2
[0217] An EVOH pellet of Comparative Example 2 was obtained in a
similar manner to Example 1 except that hot air at 150.degree. C.
was blown in place of irradiating the EVOH pellet with an infrared
ray.
Comparative Example 3
[0218] An EVOH pellet of Comparative Example 3 was obtained in a
similar manner to Example 1 except that the EVOH pellet was
irradiated with an ultraviolet ray in place of irradiating with an
infrared ray.
TABLE-US-00001 TABLE 1 Ethylene Water content Degree of content
Melting % by saponification Form % by temperature Light or heat
Wavelength*.sup.2 mole % by mole -- mass*.sup.1 .degree. C. -- nm
Example 1 32 99.98 or greater pellet 0.3 183 Infrared ray 1,100
Example 2 32 99.98 or greater pellet 0.3 183 Infrared ray 1,100
Example 3 32 99.98 or greater pellet 0.3 183 Infrared ray 1,100
Example 4 32 99.98 or greater pellet 0.3 183 Infrared ray 1,100
Example 5 32 99.98 or greater pellet 0.3 183 Infrared ray 1,100
Example 6 32 99.98 or greater pellet 0.3 183 Infrared ray 1,100
Example 7 32 99.98 or greater pellet 0.3 183 Infrared ray 1,100
Example 8 32 99.98 or greater pellet 0.3 183 Infrared ray 1,100
Example 9 32 99.98 or greater pellet 0.3 183 Infrared ray 1,100
Example 10 32 99.98 or greater pellet 0.3 183 Infrared ray 1,100
Example 11 32 99.98 or greater pellet 0.3 183 Infrared ray 1,100
Example 12 32 99.98 or greater pellet 10 183 Infrared ray 1,100
Example 13 32 99.98 or greater pellet 110 183 Infrared ray 1,100
Example 14 32 99.98 or greater pellet 110 183 Infrared ray 1,100
Example 15 32 99.98 or greater pellet 110 183 Infrared ray 1,100
Example 16 32 99.98 or greater film 0.05 183 Infrared ray 1,100
Example 17 32 -- paste -- 183 Infrared ray 1,100 Example 18 27
99.98 or greater pellet 0.3 191 Infrared ray 1,100 Example 19 48
99.98 or greater pellet 0.3 160 Infrared ray 1,100 Comparative 32
99.98 or greater pellet 0.3 183 -- -- Example 1 Comparative 32
99.98 or greater pellet 0.3 183 Heat -- Example 2 Comparative 32
99.98 or greater pellet 0.3 183 ultraviolet 365 Example 3 ray
Appearance character- Long-run Irradiation istics workability
Intensity or heating (Coloring (Viscosity W/m.sup.3 Temperature
time .DELTA.YI properties) stability) (.times.10.sup.3) .degree. C.
hr -- -- -- Example 1 330 130 to 150 1 5 A A Example 2 384 145 to
160 1 4 A A Example 3 362 140 to 160 1 4 A A Example 4 296 105 to
125 1 4 A A Example 5 272 85 to 110 1 3 A A Example 6 241 85 to 105
1 3 A A Example 7 241 75 to 95 1 3 A A Example 8 330 70 to 80 0.1 1
B A Example 9 330 130 to 150 0.5 3 A A Example 10 330 130 to 150 3
4 A A Example 11 330 130 to 150 5 3 A A Example 12 330 130 to 150 1
4 A A Example 13 330 130 to 150 1 4 A A Example 14 330 130 to 150 5
7 A A Example 15 330 130 to 150 10 6 A B Example 16 330 130 to 150
1 2 B A Example 17 1,390 60 to 80 1 -- A A Example 18 330 130 to
150 1 2 B A Example 19 330 130 to 150 1 2 B A Comparative -- -- --
0 B A Example 1 Comparative -- 130 to 150 2 -16 C C Example 2
Comparative 28 20 1 0 B A Example 3 *.sup.1value derived by
dividing the mass of water included in the pellet or film by the
dry mass of the resin included in the pellet or film. *.sup.2to be
the dominant wavelength emitted from the light source.
[0219] <Evaluation of EVOH Resin>
[0220] Evaluations of the EVOH resins of Examples 1 to 19 and
Comparative Examples 1 to 3 obtained as described above were
performed as in the following. The results of evaluation are shown
in Table 1.
[0221] (Evaluation Method)
[0222] (1) .DELTA.YI (change in the degree of coloring (yellowing)
between before and after the light or heat treatment)
[0223] YI (yellow index) values of the EVOH pellet or the EVOH film
before and after subjecting to the light or heat treatment were
measured using "LabScan XE Sensor" manufactured by HunterLab, and
the LYI value was calculated according to the following formula
(III). It should be noted that the YI value is a marker
representing the yellowness index (yellowishness) of an object.
More specifically, a higher YI value suggests a greater yellowness
index (yellowishness), whereas a smaller YI value suggests a lower
yellowness index (yellowishness) indicating being less colored.
Also, a higher .DELTA.YI value indicates that prevention of
coloring such as yellowing by a light or heat treatment is more
significantly enabled.
[ formula 3 ] .DELTA. YI = ( YI value before the treatment ) - ( YI
value after the treatment ) ( III ) ##EQU00003##
[0224] (2) Appearance Characteristics (Degree of Coloring
(Yellowing) After Light Irradiation)
[0225] The degree of coloring of the EVOH pellet or the EVOH film
produced by the aforementioned method was determined by visual
inspection as in the following.
[0226] Determination: criteria [0227] A: being favorable [0228] B:
being less yellowish [0229] C: being yellowish
[0230] (3) Long-Run Workability (Viscosity Stability)
[0231] Change in torque when 60 g of the obtained EVOH pellet was
kneaded in a Laboplast Mill (manufactured by Toyo Seiki
Seisaku-sho, Ltd. "20R200"; biaxial, counter rotating type) at 100
rpm and 260.degree. C. was measured. The torque was measured after
5 min from the beginning of kneading, and a time period was
determined which was required until the torque value reached 1.5
times the aforementioned torque value after 5 min from the
beginning. This time period being longer indicates less change in
the viscosity, and more superior long-run workability.
[0232] Determination: criteria [0233] A: 60 min or longer [0234] B:
40 min or longer and shorter than 60 min [0235] C: 20 min or longer
and shorter than 40 min
[0236] As is seen from the results shown in Table 1, it is revealed
that an EVOH resin enabling prevention of yellowing, and having
sufficient long-run workability can be obtained according to the
method for production of Examples 1 to 19.
INDUSTRIAL APPLICABILITY
[0237] The EVOH resin of the present invention can prevent coloring
such as yellowing; therefore, it can be suitably used as a material
for various types of molded products, monolayer or multilayer
films, sheets, pipes, vessels and fibers that are superior in
appearance characteristics.
* * * * *